Strain relieving device



y 14, 1942- F. c. PETERSEN STRAIN RELIEVING DEVICE Filed Feb. 15, 1940 Patented 1.1.1., 1942 UNITED STATES PATENT OFFICE STRAIN RELIEVING DEVICE Frank C. Petersen, Glen Ellyn, 1ll., assignor to George D. Ladd, Lockport, 111.

Application February 15, 1940, Serial No. 319,006

8 Claims. 01. 173-322) My invention relates to strain relieving devices for electric conductors and thelike, more particularly to devices of this character that are adapted to be applied to panels through which suitable conductors pass for connection to terminals, and that efl'ectively prevent the transmission to the terminal members of strains due to mechanical loads imposed on the. conductors, and my invention has for an object the provision of a strain relieving device which is simple and economical in its construction and reliable in its operation.

In many difl'erent types of electrical apparatus it is standard practice to provide strain relieving devices mounted on panels or on similar elements through which conductors extend, in order to prevent the conductors from being pulled loose from their terminal members due to strains which are inevitablyimposed upon the conduce tors diu'lngthe use or the installation of the apparatus. Various types of strain relieving devices have heretofore been provided, many of which havebeen to a large extent satisfactory from the standpoint that they adequately absorb the strains'and that they are readily removable or releasable. so far as I am aware, however, all of such prior devices have been so constructed as to exert on the conductor a constant pinching or clamping action which is objectionable.

since it may eventually cause deterioration and f failure of the insulation material surrounding the conductor wires.

It is thereforea further object of my invention to provide a strain relieving device which is capable of quick application and quick release, which consists of relatively few and simple parts, and which imposes no pinching or clamping action on the conductors except when a pulling force tending to move th'e'conductor longitudinally is exerted thereon.

In carrying out my invention in one form, I

7 provide means adapted to receive an electric conductor and to be rotated about an axis extending at a substantial angle to the conductor so as to form loops in the conductor partially encircling portions of the rotatable means, together with means for looking or holding the rotatable means in a position such that strains imparted to the conductors are transmitted by the loops to the rotatable means. More particularly, my improved strain relieving device comprises a base plate adapted to be secured to a suitable panel and having mounted on one face thereof an insulating member, the base plate and the member being provided with aligned conductor-receiving apertures. Suitable supporting" portions extend rearwardly from. the base plate, and a second insulating member is provided having a pair of arms extending substantially parallel to the base plate so as to provide a conductor-receiving space therebetween,

this second member being rotatably mounted by In addition, I provide stop means positioned to engage a portion .of the second member at a predetermined point in its rotation, whereupon further rotation of this member causesinward movement of the axis toward the first member to insure that the portions of the loops which lie between the two members snugly engage the arms of the second member, and releasable looking means are provided for locking or holding the second member in a predetermined strain relieving position after rotation thereto, so that strains imposed on the conductor are transmitted by the loops to the arms of the second member.

For a more complete understanding of my invention, reference should now be had to the drawing, in which:

Fig. l is a view in exploded perspective of a strain relieving device embodying my invention;

Fig. 2 is a perspective view of the device shown in Fig. 1, illustrating the parts in assembled relation'before the conductor has been threaded through the device;

Fig. 3 is a top plan view of the device shown in Figs. 1 and 2, with a conductor threaded therethrough but before the device has been operated to its strain relieving position:

Fig. its a sectional view taken along the line 4-4 of Fig, 3;

Fig. 5 is a top plan view similar to Fig. 3, but

showing the device after it has been operated to and locked in its strain relieving position; and

Fig. 6 is a sectional view taken along the line 6-6 of Fig. 5.

Referring now to the drawing, 1 have shown my invention as applied to a strain relieving dereceive suitable screws or bolts, not shown,

by means of which the base plate l8 may be secured to the panel if desired. As shown, the base plate I8 is likewise provided with a pinrality of tabs or ears I: which extend rearwardly therefrom adjacent the opposite edges of the apertures H, and which are adapted to be received in suitable notches ll in an insulating member I5 which includes a centrally located conductor-receiving aperture IS. The tabs I! may be bent over and clinched, as shown in Fig. 2, so as rigidly to secure the insulating member I5 to the base plate It when the device is assembled.

In addition to the insulating member I5, my improved strain relieving device includes a second insulating member l1, shown best in Fig. 1, which comprises a pair of spaced apart arms l8 connected together at one end by a vertically extending portion I 8 and connected'together at the opposite end by an extending portion 20, one end of the portion is extending outwardly beyond the arms I 8 to .provide a locking portion 2|,

.as will be more fully described hereinafter. In

order properly to mount the insulating member H in rotatable relation with respect to the base plate l0 and the insulating member IS, the base plate I8 is provided, as shown, with a pair of rearwardly extending supporting portions 22 and 23, each of which is provided with a slot 24 for receiving extending portions 25 of the member l'I so as to provide pin and slot connections therebetween; As shown, the outerends of the slots 28 are normally closed by wing portions 28 formed integrally with the supporting portions 22 and 23, and it will be apparent that these wing portions 28 may be temporarily bent out-. wardly in order to permit assembly of the insulating member I! with the portions 25 thereof extending into slots 24. U

Initially, the second insulating member I! occupies the position shown in Figs. 2, 3, and

4, in which position the upper portions thereof engage suitable stop lugs.2'| which extend inwardly from the supporting portions 22 and 28, and in which position the space between the arms l8 of the member I! is aligned with. the aperture IS in the insulating-member 15 so} that a suitable conductor may be readily passed through the strain relieving device, as for example the conductor 28 shown in Figs. 3to inclusive.

After the conductor 28 has been passed-through the strain relieving device, as shown in Figs. 3

and 4, the insulating member II maybe rotated about the axis provided by the pin and slot connection between the member I! and the supporting portions 22 and 23 in the directionof the arrow 29 in Fig. 4. Rotation of the member I! in this direction causes the arms l8 to engage portions of the conductor "28 on oppositesides thereof and, as the rotation continues, loops are formed in the conductor which encircle the arms l8. It will be observed that in the initial position, illustrated in Figs; 2, 3, and 4, the member I1 occupies a position remote from the inner ends of the slots 24 which permits the member II to be rotated without encountering or engaging the insulating member Hi. It will likewise be apparent, however, that when the member ll has been rotated through an angle which is substantially greater than but less than it will engage the stop lugs 2'] and further rotation of the member I! thereafter causes inward movement of the axis of rotation toward the inner ends of the slots 24 so that the member l1 pivots about the stop lugs 21 to the position illustrated in Figs. 5 and 6, in which .position the member I! is locked by engagement of the portion 2| thereof with a latch member 38 which extends inwardly from the lower edge of the supporting portion 22.

When the member I! occupies the final position shown in Fig. 6, it wiil'be observed that I opposed loops are formed in the conductor 28, which loops encircle the arms l8 so that a me-- chanical knot is formed in the conductor. Preferabiy the stop lugs 21 and the latch 38 are so located that themember I! in its final position is spacedfrom the member l5 a distance substantially equal tothe thickness of the conductor 28 so as to insure that the portions 3| of the loops, which portions are located between the members l5 and I! as shown in Fig. 6, snugly engage the arms l8 of the insulating member I]. Although no portion of the conductor 28 is positively pinched or clamped by the strain relieving device which the parts are in the position shown in Fig. 6, it will be apparent that any longitudinal forces exerted on the conductor 28 on either side of the strain relieving device will cause the opposed loops in the conductor to grip more tightly the arms l8 and thus transfer to the arms all of the strain imposed on the conductor. It is of course preferable that the arms I8 be formed with suitable rounded edges, as shown, so as to eliminate any tendency to cut or damage the insulation on the conductor 28. In. actual tests of a device constructed as illustrated in the drawing, a weight of 35 pounds was applied to a conductor for a period of two hours without re sulting in any cutting or damaging of the insulating material on the conductor.

When it is desired to release the conductor 28 for the purposes of rewiring or for any purpose which'requires varying the position of the conductor 28 with respect to the strain release device, it is only necessary to press outwardly on the lower edge of the supporting portion 22 so as to release the latch 80 from engagement with the portion 2| of the; insulating member l1, whereupon the member KILmay-be rotated in a reverse direction, 1. e., a clockwise direction as viewed in Fig. 6, so as to return the member H to the initial position illustrated in Figs. 2, 3, and 4.

Preferably the base plate 18 and the supporting portions 22 and 23,, together with the tabs IS,

the wings 26, the-stop lugs 21,-and the latch 38,

are formed from a single piece of sheet metal by means of a suitable stamping operation, and the various parts thereafter bent so as to assume the relative shapes and positions shown in Fig. 1. It will now be apparent that I have provided an improved strain relieving device consisting of a relatively few parts and which may be quickly assembled, which may be readily operated to a strain relieving or locked position and quickly released therefrom when desired, and which is effective to absorb strains imposed on the conductor without exertinga constant pinching or clamping action on the conductor.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

Having thus described my invention, what I .claim and desire to secure by Letters Patent is:

1. A strain relieving device for securing an electric conductor or the like against longitudinal movement with respect thereto to prevent transmission of strains to conductor portions therebeyond when the conductor is subjected to longitudinal forces, comprising a member having a conductor-receiving aperture through which a conductor is adapted to pass freely when said member is in one position, means mounting said member for rotation from said one position to a second position about an axis substantially normal to the axis of said aperture, portions of said member on opposite sides of said aperture engaging the conductor during said rotation to form opposed loops in the conductor, and means for locking said member in said second position against return movement due to forces exerted tudinal forces, comprising a member having a conductor-receiving aperture through which a conductor is adapted topass freely when said member is in one position, means mounting said member for rotation from said one position to a second position about an axis extending through saidaperture substantially normal to the axis of said aperture, portions of said member on opposite sides of said aperture engaging the conductor during said rotation to form opposed loops in the conductor, and means for locking said member in said second position against return movement due to forces exerted on the conductor whereby strains imposed on said conductor are transmitted to said member by said loops and are absorbed by said locking and said mounting means, said locking means being manually releasable to permit 'return movement of said member to said one position to release said conductor for longitudinal movement with respect to said device.

3. A strain relieving device for securing an electric conductor or the like against longitudinal movement with respect thereto to prevent transmission of strains to conductor portions there'- beyond when the conductor is subjected to longitudinal forces, comprising a member having a pair of arms spaced apart to permit a conductor to pass therebetween, means mounting said member for rotation about an axis intermediate said arms and substantially parallel thereto whereby said arms engage portions of said conductor on opposite sides of said axis and form opposed loops therein, and means for locking said member in a position substantially 180 from its initial position to cause said opposed loops to encircle said arms on at least three sides whereby strains imposed on said conductor ,are transmitted to said arms by said opposed loops, said locking means preventing reverse, movement of said member by strains transmitted thereto from said conductor.

4. A strain relieving device for securing an electric conductor or the like against longitudinal movement with respect thereto to prevent transmission of strains to conductor portions therebeyond when the conductor is subjected to longitudinal forces, comprising a fixed member having a conductor-receiving aperture, 2. second member having a pair of arms spaced apart to permit a conductor passing through said aperture to extend freely therebetween substantially normal to said arms, means mounting said second member rearwardly of said fixed member for rotation about an axis located in a plane through said arms, said axis being substantially parallel to and between said arms whereby said arms engage portions of said conductor on opposite sides of said second member and upon rotation of said member through an angle substantially greater than form opposed loops in said conductor about said arms, one of said arms during said movement passing across said aperture in said fixed member, and releasable means for normally holding said second member in its rotated position against the forces exerted thereon by strains imparted to said conductor.

5. A strain relieving device for electric conductors and the like comprising a base plate, a first insulating member secured thereto, said member and said plate having aligned conductor-receiving apertures therethrough, supporting portions extending rearwardly of said base plate on opposite sides of said first member, a second insulating member having a pair of arms extending substantially parallel to said base plate and providing a conductor-receiving space therebetween, means including pin-and-slot connections between said second member and said supporting portions for mounting said second member with said space aligned with said apertures whereby a conductor may be freely passed through said device, said mounting means providing for rotation of said second member about an axis m0vable toward and away from said base plate, said arms upon rotation of said second member engaging said conductor on opposite sides of the axis of rotation to form opposed loops therein about said arms, stop means positioned to engage a portion of said second member at a predetermined point in said rotation, whereupon further rotation of said second member causes inward movement. of said axis toward said first member to insure that the portions of said loops between said members snugly engage said arms, and means for locking said second member in a predetermined strain relieving position wherein strains imposed on said conductor are transmitted to said arms by said loops.

6. A strain relieving device comprising a fixed member .having a conductor-receiving aperture, a second member having a pair of arms spaced apart to permit a conductor passing through said aperture to extend therebetween, means mounting said second member rearwardly of said fixed member for bodily movement toward and awayfrom said fixed member and for rotation about an axis substantially parallel to said arms and to said fixed member, said arms upon rotation engaging said conductor on opposite sides of the conductor is adapted to extend, means mounting U a second one of said members rearwardly of said one member with the apertures in said members substantially aligned so that said conductor may be freely drawn therethrough, means for'rotating said second member to engage said conductor on opposite sides of the aperture through said second member and form opposed loops in said conductor whereby strains imposed on said conductor are transmitted to said second member by said loops, and means for locking said second member in its rotated position to prevent reverse movement of said member by said strains.

8. A strain relieving device for securing an azeaoea electric conductor or the like against longitudinal movement with respect thereto to prevent transmission of strains to conductor portions therebeyond when the conductor is subjected to longitudinal forces, comprising a pairor members having apertures for permitting a conductor to pass therethrough, means mounting one of said members rearwardly of the other member -with the apertures in said members substantially aligned so that said conductor may be freely drawn therethrough, means for rotating said one member to engage said conductor on opposite sides of the aperture through said one member and form opposed loops in said conductor whereby strains imposed on said conductor are transmitted to said one member by said loops, and means for locking said one member in its rotated position to prevent reverse movement of said one member by said strains.

FRANK C. PETERSEN. 

